用vector没用queue爆MLE求改

#include <iostream>
#include<cstring>
#include <cmath>
#include <vector>
#include <utility>
short n,m;
short start_x,start_y;
short ** map;
short max_step;

short incre_x[8]={-2,-1,1,2,2,1,-1,-2};
short incre_y[8]={-1,-2,-2,-1,1,2,2,1};

void draw(void)
{
    for(short i=0;i<n;i++)
    {
        for(short j=0;j<m;j++)
            std::cout<<map[i][j]<<' ';
        std::cout<<std::endl; 
    }
    std::cout<<std::endl; 
}

void bfs(short **ma,short step,std::vector<std::pair<short,short> >& arr)
{
    if(step>max_step)
        return ;
    int num=arr.size();
    std::vector<std::pair<short,short> > arr_next;
    //std::cout<<num<<std::endl;
    for(int i=0;i<num;i++)
    {
        ma[arr[i].first][arr[i].second]=step;
        for(short j=0;j<8;j++)
        {
            if(arr[i].first+incre_x[j]>=0&&arr[i].first+incre_x[j]<n&&arr[i].second+incre_y[j]>=0&&arr[i].second+incre_y[j]<m&&ma[arr[i].first+incre_x[j]][arr[i].second+incre_y[j]]==-1)
            {
                arr_next.push_back(std::make_pair(arr[i].first+incre_x[j],arr[i].second+incre_y[j]));
            }
        }
    }
    //draw();
    arr.clear();
    bfs(ma,step+1,arr_next);
}

int main (void)
{
    std::cin>>n>>m>>start_x>>start_y;

    map=new short * [n];

    for(short i=0;i<n;i++)
    {
        map[i]=new short[m]();
        memset(map[i],-1,sizeof(short)*m);
    }

    max_step=std::max(n,m);
    std::vector<std::pair<short,short> > arr;
    arr.push_back(std::make_pair(start_x-1,start_y-1));
    bfs(map,0,arr);
    //std::cout<<max_step<<std::endl;
    for(short i=0;i<n;i++)
    {
        for(short j=0;j<m;j++)
            std::cout<<map[i][j]<<' ';
        std::cout<<std::endl; 
    }

    return 0;
 }